An electron beam diffraction pattern is used for adjusting the crystal orientation of a sample using a transmission electron microscope. Adjusting the electron beam incidence direction and the direction of the crystal axis makes it possible to acquire atomic column information and identify the crystal. In addition, when ascertaining the structure of polycrystalline particles in the vicinity of an interface, it is possible to accurately obtain the particle boundary width or the like by setting a crystalline particle boundary and an electron beam axis in parallel. For example, when evaluating the structure of a semiconductor device, in order to accurately measure the length of structural object which is laminated on a Si substrate, the crystal orientation of the Si substrate is adjusted and the sample is tilted such that electron beams are incident thereto in parallel with the substrate surface.
While the adjustment of the crystal orientation is an essential technique when using a crystalline sample, expertise is required in order to accurately adjust the crystal orientation while observing the electron beam diffraction pattern.
Here, the crystalline sample refers to a sample of which apart or all has an ordering. Examples of samples include single crystals, polycrystals which are complexes of a plurality of fine crystals, or quasicrystals. In addition, compounds which are formed of a single element or a plurality of elements may also be included in the crystalline sample.
In PTL 1, regarding the adjustment of the crystal orientation, electron beam diffraction pattern data which is acquired for each tilting angle of the sample is stored in advance, a distribution of spots of the electron beam diffraction pattern is fitted in a circle based on the stored data, and the sample is automatically tilted such that the radius of the circle is minimized. In addition, for a plurality of electron beam diffraction patterns, a trajectory of a central coordinate of an approximate circle which is determined for each pattern is approximated to a primary function, and a sample tilting angle which is able to obtain an intersection on a primary function straight line at the shortest distance between the primary function straight line and a direct spot central coordinate is determined and set as the optimum tilting angle.